1. Technical Field
The present invention relates to an optical touch system and an image processing method thereof.
2. Related Art
An optical touch system generally comprises an imaging device, an illuminating device, and a computing device for determining the touch position of an object. Typically, the object may be a finger, a stylus, or the like. The imaging device is configured to view a touch zone above a touch surface. The illuminating device is configured such that when an object is in the touch zone, the illuminating device can make the object generate an identifiable contrast image on a picture produced by the imaging device. The computing device is configured to calculate the coordinates of the object according to the brightness variation of the picture produced by the imaging device.
The optical touch system can be designed as a system in which the object entering into the touch zone blocks the light projected from the illuminating device so as to form a dark area on the imaging device, or as a system in which the object reflects the light projected from the illuminating device to form a bright area. Regardless of which system is employed, the current coordinate calculating method requires two pictures, a background picture and a picture taken when there is an object in the touch zone. Normally, the background picture is generated and stored before operation. The optical touch system can identify the region having obviously different intensity by comparing the captured picture and the background picture. When the region having obviously different intensity is used as an image formed by an object, the optical system can calculate the coordinates of the object according to some features of the region having obviously different intensity.
In addition to the region having obviously different intensity, the intensity levels of a portion of the background area of the picture may be changed due to the change of the light path or the manner of light reflection of the touch surface caused by the object such that a difference may occur between a background area of the picture and the corresponding portion of the background picture. Such difference may make it impossible for the region having obviously different intensity to be correctly calculated or properly identified. As a result, the coordinates of the object cannot be accurately calculated.